Flesh out xpdjoj.org overview for this session

[tobyweston]

Each session gets an overview page on https://xpdojo.org. These are marketing collaterals for the public but also reminders for us in terms of structure and goals.

Need to flesh out this one https://xpdojo.org/docs/lessons/03/cdc.html. In particular, the structure/timings etc.

• structure section with timings
• location of slides (so they can be run from any instructors machine)